In the field of off-highway trucks used in mining operations, for example, it is desirable that an accurate record be kept of the quantity of material removed from the mining site. This information can be used to calculate mine and truck productivity as well as aid in forecasting profitability and work schedules.
Other systems, as disclosed in U.S. Pat. No. 4,635,739 issued to D. Foley et al. on Jan. 3, 1987, have shown that strut pressure can be an accurate indicator of payload. The apparatus disclosed therein includes an electronic control which monitors each of the strut pressures, compensates for various inaccuracies introduced by load distribution and vehicle attitude, and correlates this information into actual payload. This payload information allows the truck to be operated efficiently near its maximum capacity without promoting undue vehicle wear. An overloaded vehicle hastens tire and frame damage.
Operation of the vehicle with a collapsing strut will have detrimental effects on the accuracy of the payload monitor because of the change in the relationship between strut pressure and payload. Other serious consequences also result from such operation. For example, uneven tire wear is an undesirable result of extended vehicle operation with a collapsed strut. Tires are a major operating expense of off-highway trucks and any increase in their replacement schedule impacts on profitability. Thus a collapsed strut can have economic impact other than replacement of the damaged strut. Moreover, a completely collapsed strut results in repeated metal-to-metal contact which can cause frame damage in relatively short periods of operation. Resultant repair costs are exorbitant.
Operation of the vehicle with an underinflated tire, while not necessarily causing payload inaccuracies, results in tire damage because it wears at an accelerated rate. Additionally, tires on off-highway trucks tend to have very stiff sidewalls, so visual inspection rarely detects an underinflated condition.
The present invention is directed to overcoming one or more of the problems as set forth above.